Overvoltage protection for series capacitors consists primarily of a large bank of varistors connected in parallel. Depending on the desired protection levels, temporary overvoltage conditions and the energy absorption capability, the varistors are built up of multiple columns of series-connected ZnO blocks.
The varistors in the bank may be housed in porcelain or silicone rubber. The former has the advantage of accommodating multiple columns in each housing. The latter has the advantage of flexible and easy erection combined with compactness and low weight in the form of rack assembly. This low weight alternative has a great advantage when expensive EHV insulated platforms are to be designed for accommodating them.
The MXE racks are pre-assembled for easy and quick connection at the site.